Systems and methods for implantation of spinal plate

ABSTRACT

A method includes tracking one or more of a plurality of bones of a patient, adjusting a relationship between the plurality of bones to a desired rotation between the plurality of bones, and creating an implant placement plan based on the relationship. The implant placement plan includes a placement of a plate across the plurality of bones. The method also includes robotically assisting preparation of the plurality of bones to receive the plate in accordance with the implant placement plan.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/736,614, filed Jan. 7, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/025,462, now U.S. Pat. No. 10,568,698, filedJul. 2, 2018, which is a divisional of U.S. patent application Ser. No.14/586,192, now U.S. Pat. No. 10,034,711, filed Dec. 30, 2014, whichclaims the benefit of and priority to U.S. Provisional PatentApplication No. 61/922,627, filed Dec. 31, 2013, each of which is herebyincorporated by reference in its entirety.

BACKGROUND

The present invention relates to a surgical system and, moreparticularly, to a surgical system and method for spinal implantprocedures, such as cervical or lumbar discectomy.

Instability of the human spine often calls for the implantation ofspinal plates. In the cervical spine, instability may be caused bytrauma or deformities, such as curves of the spine, or instabilityassociated with corpectomy for disc disease or with reconstructivesurgeries for, as an example, tumors of the cervical spine. A spinalplate, typically used in conjunction with a disc or vertebral prosthesisor a spinal cage/spacer, is used to provide stability between adjacentvertebrae, as well as to maintain a desired rigid relationship betweenthe adjacent vertebrae. Present spinal plates may have a protrudingprofile when implanted on the spine. For example, a cervical plate oftenprotrudes and causes discomfort for patients. Patients may experiencedifficulty swallowing, and may feel pressure at their throat. Similarly,protruding plates in the lumbar spine may affect the vascular anatomy inthe lower lumbar area. Thus, as an alternative in order to lessen theprotrusion of spinal plates, some plates have been designed to be lessrobust. Plates have been made to be thinner, and therefore less strong,in favor of a lower profile.

Generally, implantation of spinal plates has not been widely performedusing computer-assisted surgery systems. The functions of acomputer-assisted surgery (CAS) system may include pre-operativeplanning of a procedure, presenting pre-operative diagnostic informationand images in useful formats, presenting status information about aprocedure as it takes place, and enhancing performance.

Robotic systems are often used in applications that require a highdegree of accuracy and/or precision, such as surgical procedures orother complex tasks. Such systems may include various types of robots,such as autonomous, teleoperated, and interactive. For some types ofsurgery, such as joint replacement surgery, interactive systems arepreferred because such systems enable a surgeon to maintain direct,hands-on control of the surgical procedure while still achieving a highdegree of accuracy and/or precision. For example, in knee replacementsurgery, a surgeon can use an interactive, haptically guided robotic armin a passive manner to sculpt bone to receive a joint implant, such as aknee implant. To sculpt bone, the surgeon manually grasps andmanipulates the robotic arm to move a cutting tool (such as a burr) thatis coupled to the robotic arm to cut a pocket in the bone. As long asthe surgeon maintains a tip of the burr within a predefined virtualcutting boundary defined, for example, by a haptic object, the roboticarm moves freely with low friction and low inertia such that the surgeonperceives the robotic arm as weightless and can move the robotic arm asdesired. If the surgeon attempts to move the tip of the burr to cutoutside the virtual cutting boundary, however, the robotic arm provideshaptic (or other force) feedback that prevents or inhibits the surgeonfrom moving the tip of the burr beyond the virtual cutting boundary. Inthis manner, the robotic arm enables highly accurate, repeatable bonecuts.

SUMMARY

One embodiment of the invention relates to a method for implanting aspinal plate during a surgical procedure. The method includes the stepsof displaying information about a spinal target region of a patientincluding target vertebrae on which the implantation is to be performed,inserting a spacing device between two adjacent vertebrae to achieve adesired relationship between the vertebrae, planning placement of aspinal plate on the spinal target region to maintain the desiredrelationship between two adjacent vertebrae. The desired relationshipmay include one of a desired orientation of a first vertebrae withrespect to a second vertebrae and a desired configuration of a vertebraldisc space between the first and second vertebrae. The method furtherincludes defining a virtual cutting boundary on a virtual representationof each of the first and the second vertebrae according to the plannedplacement of the spinal plate on the spinal target region. The methodfurther includes tracking a position of the surgical cutting tool heldby a haptic device as the surgical cutting tool is manually moved by auser to form a sculpted cavity independently on each of the first andthe second vertebrae for receiving the spinal plate, and providinghaptic feedback to the user indicative of interaction between thesurgical cutting tool and the virtual cutting boundary. The sculptedcavity formed according to the virtual cutting boundary may have a depththat is greater than or substantially equal to the thickness of spinalplate. The method may also include implanting the spinal plate on thetarget vertebrae within the sculpted cavity, such that a top surface ofthe spinal plate is substantially flush with the surface of the targetvertebrae. The virtual cutting boundary may correspond to the shape ofthe spinal plate and the virtual cutting boundary may correspond to thedimensions of the spinal plate. In this method, the surgical cuttingtool may be a surgical burr.

The spinal target region for implantation of the spinal plate may be thecervical region of the spine or may be the lumbar region of the spine.The sculpted cavity may span between two adjacent vertebrae, and mayfurther include a portion of the intervertebral disc space between thetwo adjacent vertebrae. The sculpted cavity may also further include aplurality of predrilled holes for receiving an engagement member toengage the spinal plate with the bone.

The method of implanting a spinal plate may further include displayingan anatomical image of the anatomy of the patient including arepresentation of the surgical cutting tool as the surgical cutting toolmoves during the surgical procedure.

Another embodiment of the invention relates to a surgical system forimplanting a spinal plate, comprising a surgical device holding asurgical tool configured to be manipulated by a user to perform animplantation procedure on a patient and a computer system. The computersystem is programmed to associate a virtual object with a desired cavityto be sculpted in a first vertebrae and an adjacent second vertebrae ofthe patient's spine to enable the surgical device to provide a limit onuser manipulation of the surgical tool, based on a relationship betweena position of the surgical tool and the desired sculpted cavity. Thesurgical device includes at least one feedback mechanism configured tosupply feedback to the user manipulating the surgical device, and thecomputer system further programmed to control the at least one feedbackdevice to provide the limit on user manipulation, based on arelationship between a position of the surgical tool and the desiredsculpted cavity. The virtual object is associated with the desiredcavity that is sized and configured to receive the spinal plate therein,according to a planned placement of the spinal plate to achieve adesired relationship between two adjacent vertebrae. The desiredrelationship may include one of a desired orientation of a firstvertebrae with respect to a second vertebrae and a desired configurationof a vertebral disc space between the first and second vertebrae. Thedesired cavity may be sized and configured such that the spinal platehas a minimal profile above the surface of the patient's spine whenimplanted.

The system may further include a detection device for determining a poseof an object, and may also include at least one trackable elementdetectable by the detected device and configured to be attached to anobject to be tracked. The system may also include a display device andwherein the computer system is further programmed to display on thedisplay device at least one of a representation of the target portion ofthe patient's spine, a representation of the spinal plate implanted onthe patient's spine, a representation of the virtual object on therepresentation of the anatomy, and a representation of the surgical toolon the representation of the anatomy as the surgical tool moves duringthe surgical procedure.

The surgical tool may be a cutting burr. The computer system further mayinclude a database of spinal plate models such that the virtual objectcan be associated with the desired cavity that corresponds to the shapeand size of the particular spinal plate to be used.

Another embodiment of the invention relates to a spinal plate system.The system comprises a spinal plate having a particular shape and size,a surgical device configured to be manipulated by a user, a surgicaltool coupled to the surgical device; and a computing system. Thecomputing system is configured to enable a user to plan placement of thespinal plate on a spinal target region to achieve a desired relationshipbetween two adjacent vertebrae on a spine of a patient, define a virtualcutting boundary on each of the first and the second vertebrae accordingto the planned placement of the spinal plate on the spinal targetregion, and manipulate the surgical device to prepare a cavityindependently on each of the first and the second vertebrae, wherein theshape and size of the cavity corresponds to the shape and size of thespinal plate in the planned placement. The computing system is furtherconfigured to provide a limit on user manipulation of the surgical tool,based on a relationship between a position of the surgical tool and thevirtual cutting boundary.

Though the present disclosure refers primarily to spinal plates forimplantation between adjacent vertebrae, it is contemplated that thepresent systems and methods can be applied to other applications whereinit is necessary to maintain a desired relationship between two or morebones. Other applications wherein the disclosed systems and methods maybe utilized include, but are not limited to, ankle, hand/wrist, andother joint fusion procedures, and craniofacial fusion procedures.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated and constitute part ofthis specification, illustrate exemplary embodiments of the invention.

FIG. 1 is a side view of a spinal plate according to the prior artimplanted on the cervical spine.

FIG. 2 is a perspective view of a spinal plate according to an exemplaryembodiment.

FIG. 3 is a perspective view of a spinal cage inserted between adjacentvertebra and a tracker coupled thereto prior to preparation of the boneto receive a spinal plate.

FIG. 4 is a perspective view of a portion of a cervical spine preparedfor implantation of a spinal plate.

FIG. 5 is a perspective view of a portion of a cervical spine having aspinal plate according to an exemplary embodiment implanted thereon.

FIG. 6 is a perspective view of an embodiment of a surgical systemaccording to an exemplary embodiment.

FIG. 7 is a block diagram of a model surgical system according to anexemplary embodiment.

FIG. 8 illustrates a mechanical tracker to track the position of thesurgical cutting tool relative to the anatomy according to an exemplaryembodiment.

FIG. 9 illustrates steps of a spinal plate implantation procedureaccording to an exemplary embodiment.

DETAILED DESCRIPTION

A number of exemplary embodiments of the invention are illustrated inthe drawings. An effort has been made to use the same or like referencenumbers throughout the drawings to refer to the same or like parts.Although this specification refers primarily to a robotic system forcervical and lumbar spinal plate implantation, it should be understoodthat the subject matter described herein is applicable to other types ofrobotic systems and methods, including for other spinal applications.

Referring to FIG. 1 , a spinal plate 110, according to currently useddevices and methods, is shown implanted on a patient's cervical spine100. The figure depicts the use of the spinal plate positioned to spanfrom the 4^(th) to the 5^(th) cervical vertebrae 104, 105, respectively.As shown, the cervical plate 110 protrudes beyond the anterior surface100 a of the cervical vertebrae. For certain patients, this may causediscomfort and potential functional problems (e.g., choking and/orswallowing problems). Similar protrusion may occur with implanted plateson the lumbar spine, which also may cause discomfort and may impact thecomplex vasculature in the lumbar spine region.

Referring to FIG. 2 , a spinal plate 10 according to exemplaryembodiments of the present invention is sized and configured tosubstantially reduce the protrusion of the spinal plate 10 from thevertebrae surface, in connection with the surgical system and methodsdescribed below. In the embodiment shown, the spinal plate 10 includes afront surface 12 and a back surface 14. The back surface 14 isconfigured to be placed in contact with the target vertebrae, such ascervical vertebrae C4 and C5, and span across the intervertebral discspace (shown more particularly in FIG. 5 ). The spinal plate 10 includesa plurality of engagement apertures 16 for receiving an engagementmember 18, such as a screw 19. In the embodiment shown, the spinal plate10 has two apertures 16 near the top of the plate 10 and two apertures16 near the bottom of the plate 10 for a total of four apertures, forreceiving four engagement members 18. The engagement member 18, such asscrew 19, is configured to pass through the engagement aperture 16 fromthe front surface 12 through the back surface 14, to engage with a holepredrilled in the target vertebrae, and to secure the plate 10 to thevertebrae.

The spinal plate 10 is preferably made of a lightweight, strongmaterial, such as titanium. The spinal plate 10 is of a sufficientthickness to maintain the necessary strength to withstand the forces andpressures on the spinal column without faltering or wearing down. Theplate may also be made of a highly porous material, such as the PourousStructured Technology (PST™) used by MAKO Surgical Corp., to providehigh friction for stability and fit, and unique scaffold configurationfor cell access. In a preferred embodiment, the spinal plate 10 isthicker than 2.6 mm. This thickness is usually not feasible or desirabledue to the profile above the spinal vertebrae surfaces, but can beachieved with spinal plate 10 implanted according to the methodsdescribed below.

Prior to implanting the spinal plate 10, a procedure to remove tissuefrom the disc space is performed. In some cases, it is necessary toclean out diseased annulus tissue. In other cases, a full vertebral bodymay be removed in a corpectomy procedure. A space is created betweenvertebrae to receive a spinal cage or spacer, such as cage 20 shown inFIG. 3 . Cage 20 is also used in procedures to correct curves of thespine, such as to create a desired distance between portions of adjacentvertebrae to produce improved alignment. With the insertion of a cage 20between adjacent vertebrae, a desired relationship between the first andsecond vertrebra can be achieved. The desired relationship may be adesired distance between the two vertebrae (or the height of theintervertebral space), or may be some other relationship of the firstvertebrae relative to the second, such as the alignment or the relativerotation between the two (or to prevent changes in the naturallyoccurring relationship between the adjacent vertebrae, which may be thenecessity of the surgical procedure). FIG. 3 depicts cage 20 inserted invertebral disc space between two adjacent vertebrae to achieved adesired relationship therebetween.

In order to achieve the desired relationship, a first cage 20 may bereplaced by a second cage having, for example, a different height, anddifferent cages may be trialed in the space until the proper cage isfound to achieve the desired relationship. In some embodiments, the cage20 may be adjustable, i.e. expandable or adjustable by way of a hinge,to change the height and obtain the desired relationship by adjustingthe characteristics of the cage 20. This may be done prior to insertingthe cage 20 into the space, or while the cage 20 is positioned betweenthe vertebrae.

In some embodiments, the cage 20 may be further configured to measureforces being applied by each of the adjacent vertebrae. Such informationmay be useful to understand the conditions of the spine and assist withplanning implantation of the spinal plate or other prosthetic componentsto correct injury, disease or disfigurement of the spine. In oneexample, an expanding cage can include one or more force sensors tomeasure the force being applied between the vertebrae as the height ofthe cage is being manipulated. In this way, the expanding cage can beused as a sort of jack to increase the distance between the vertebraeand measure the force. The force applied between the vertebrae can bemeasured by a variety of force sensors and measuring apparatuses inassociation with the cage 20.

Once the cage 20 is inserted and achieves the desired relationshipbetween the adjacent vertebrae, a tracking array 22 may be attached tothe cage 20. The tracking array 22 is used to track the position of thecage 20 and the bones (adjacent vertebrae) that are registered thereto,to continuously understand the position and orientation of the vertebraeso that bone preparation to receive the spinal plate 10 can be achievedaccording to a surgical plan. The tracking system used for this purpose,registration of the bone relative to the tracking array 22, andpreparation of the surgical plan to prepare the bone for the spinalplate are discussed in greater detail later in this description.

As shown in FIGS. 4 and 5 , the spinal plate 10 is configured to bereceived by a sculpted area of bone, which are portions of the bone thathave been prepared according to the surgical plan, and based on guidanceprovided by the tracked position of the bones and the surgical system 30described below. In particular, the spinal plate 10 can be receivedwithin a sculpted cavity 24, formed by cavity portions 24 a, 24 b, inthe two adjacent vertebrae prepared for receiving the plate 10, as shownin FIG. 4 . As shown, the cavity 24 corresponds in shape to the plate10, such as the hourglass shape of the embodiment shown. Further, thecavity 24 is formed to correspond to a planned placement of the spinalplate 10 in order to help maintain the desired relationship between thetwo adjacent vertebrae. For example, FIG. 5 may represent the desiredrelationship between the first and the second vertebrae, which thespinal plate is intended to help maintain. Accordingly, each of thecavity portions 24 a, 24 b is formed in such a way so as to receive thespinal plate 10 that will secure the vertebrae in the desiredconfiguration. Each of cavity portion 24 a and 24 b is formedindependent of the other. In this way, when the spinal plate 10 isimplanted in the spine, the implanted spinal plate will hold theadjacent vertebrae in the desired relationship to one another.

There may also be one or more predrilled holes 26 also formed in thebone, corresponding to the number and placement of apertures 16 in theplate 10. Once the sculpted cavity 24 has been formed, the spinal plate10 can be positioned in the cavity 24 and secured to the bone by atleast one engagement member 18. As shown in FIG. 5 , in some preferredembodiments, the front surface 12 of the spinal plate 10 issubstantially aligned with the surface of the vertebrae, or ispositioned within the cavity 24. In this way, there is little to nosubstantial protrusion of the plate out from the surface of the bone.Thus, the discomfort and risks associated with the plate are minimized,while the plate still is robust enough to maintain the strength anddurability needed in spinal applications. In other embodiments, thespinal plate 10 may protrude from the surface of the bone, butnevertheless, the implantation of the plate 10 into the cavity 24diminishes at least some of the discomfort and other risks associatedwith spinal plates 10 that are wholly positioned on and protrude from anouter portion of the bone

The size, shape, and depth of the cavity 24 sculpted in the bone can beformed to correspond with the various shapes or thicknesses of a varietyof differently configured spinal plates 10. Alternatively, a cavity 24having a general shape with appropriate dimensions to receive the spinalplate 10 may be sculpted into the bone without particular regard to theexact shape of the spinal plate 10.

In certain configurations, the spinal plate and the related systems andmethods may be used to secure more than two adjacent vertebrae. In someconfigurations, the spinal plate may be configured to span more than twovertebrae, to provide for the desired relationship between, for example,three, four, five etc. vertebrae along the spine. During surgicalplanning (described in further detail below), the appropriate spinalplate is selected and the cavity in the bone is formed in order toaccommodate a spinal plate spanning three or more vertebrae. In otherconfigurations, a series of a plurality of spinal plates may be used tosecure relative alignment and spacing between a series of vertebrae. Inthis way, a first spinal plate, such as spinal plate 10, can bepositioned to span a first and a second vertebrae, and a second spinalplate spans from the second to the third vertebrae. Surgical planning isthen performed to prepare two cavities in, for example, the secondvertebrae, to accommodate a portion of both the first and the secondspinal plates.

FIG. 6 shows an embodiment of an exemplary surgical system 30 in whichthe techniques described above can be implemented. Such an exemplarysystem is described in detail, for example, in U.S. Pat. No. 8,010,180,issued Aug. 30, 2011, which is hereby incorporated by reference hereinin its entirety. The surgical system 30 includes a computing system 32,a haptic device 34, and a navigation system 36. In operation, thesurgical system 30 enables comprehensive, intraoperative surgicalplanning, such as planning placement of the spinal plate 10 to achieve adesired relationship between two adjacent vertebrae. The surgical system30 also provides haptic guidance to a user (e.g., a surgeon) and/orlimits the user's manipulation of the haptic device 34 as the userperforms a surgical procedure.

The computing system 32 includes hardware and software for operation andcontrol of the surgical system 30. Such hardware and/or software isconfigured to enable the system 30 to perform the techniques describedherein. The computing system 32 includes a surgical controller 42, adisplay device 44, and an input device 46. Referring to FIG. 7 , in anexemplary embodiment, the surgical controller 42 includes a processingcircuit 50 having a processor 52 and memory 54. Processor 52 can beimplemented as a general purpose processor, an application specificintegrated circuit (ASIC), one or more field programmable gate arrays(FPGAs), a group of processing components, or other suitable electronicprocessing components. Memory 54 (e.g., memory, memory unit, storagedevice, etc.) is one or more devices (e.g., RAM, ROM, Flash-memory, harddisk storage, etc.) for storing data and/or computer code for completingor facilitating the various processes described in the presentapplication. Memory 54 may be or include volatile memory or non-volatilememory. Memory 54 may include database components, object codecomponents, script components, or any other type of informationstructure for supporting the various activities described in the presentapplication. According to an exemplary embodiment, memory 54 iscommunicably connected to processor 52 and includes computer code forexecuting one or more processes described herein. The memory 54 maycontain a variety of modules, each capable of storing data and/orcomputer code related to specific types of functions. In one embodiment,memory 54 contains several modules related to surgical procedures, suchas a planning module 540, a navigation module 542, a registration module544, and a robotic control module 546. One such module may contain aconfiguration database in which spinal plate information is storedincluding dimensions of various spinal plates, to be used for surgicalplanning of the sculpted area of bone.

Referring still to FIG. 7 , the surgical controller 42 further includesa communication interface 56. The communication interface 56 can be orinclude wired or wireless interfaces (e.g., jacks, antennas,transmitters, receivers, transceivers, wire terminals, etc.) forconducting data communications with external sources via a directconnection or a network connection (e.g., an Internet connection, a LAN,WAN, or WLAN connection, etc.).

The surgical controller 42 may be any known computing system but ispreferably a programmable, processor-based system. For example, thesurgical controller 42 may include a microprocessor, a hard drive,random access memory (RAM), read only memory (ROM), input/output (I/O)circuitry, and any other known computer component. The surgicalcontroller 42 is preferably adapted for use with various types ofstorage devices (persistent and removable), such as, for example, aportable drive, magnetic storage, solid state storage (e.g., a flashmemory card), optical storage, and/or network/Internet storage. Thesurgical controller 42 may comprise one or more computers, including,for example, a personal computer or a workstation operating under asuitable operating system and preferably includes a graphical userinterface (GUI).

The display device 44 is a visual interface between the computing system32 and the user. The display device 44 is connected to the surgicalcontroller 42 and may be any device suitable for displaying text,images, graphics, and/or other visual output. For example, the displaydevice 44 may include a standard display screen (e.g., LCD, CRT, plasma,etc.), a touch screen, a wearable display (e.g., eyewear such as glassesor goggles), a projection display, a head-mounted display, a holographicdisplay, and/or any other visual output device. The display device 44may be disposed on or near the surgical controller 42 (e.g., on the cartas shown in FIG. 6 ) or may be remote from the surgical controller 42(e.g., mounted on a stand with the navigation system 36). The displaydevice 44 is preferably adjustable so that the user canposition/reposition the display device 44 as needed during a surgicalprocedure. For example, the display device 44 may be disposed on anadjustable arm (not shown) or to any other location well-suited for easeof viewing by the user. As shown in FIG. 6 there may be more than onedisplay device 44 in the surgical system 30.

The display device 44 may be used to display any information useful fora medical procedure, such as, for example, images of anatomy generatedfrom an image data set obtained using conventional imaging techniques,graphical models (e.g., CAD models of spinal plates, such as spinalplate 10, implants, instruments, anatomy, etc.), graphicalrepresentations of a tracked object (e.g., anatomy, tools, spinalplates, such as spinal plate 10, implants, etc.), constraint data (e.g.,axes, articular surfaces, etc.), representations of implant components,spinal plates, such as spinal plate 10, digital or video images,registration information, calibration information, patient data, userdata, measurement data, software menus, selection buttons, statusinformation, and the like.

In addition to the display device 44, the computing system 32 mayinclude an acoustic device (not shown) for providing audible feedback tothe user. The acoustic device is connected to the surgical controller 42and may be any known device for producing sound. For example, theacoustic device may comprise speakers and a sound card, a motherboardwith integrated audio support, and/or an external sound controller. Inoperation, the acoustic device may be adapted to convey information tothe user. For example, the surgical controller 42 may be programmed tosignal the acoustic device to produce a sound, such as a voicesynthesized verbal indication “DONE,” to indicate that a step of asurgical procedure is complete. Similarly, the acoustic device may beused to alert the user to a sensitive condition, such as producing atone to indicate that a surgical cutting tool is nearing a criticalportion of soft tissue.

The input device 46 of the computing system 32 enables the user tocommunicate with the surgical system 30. The input device 46 isconnected to the surgical controller 42 and may include any deviceenabling a user to provide input to a computer. For example, the inputdevice 46 can be a known input device, such as a keyboard, a mouse, atrackball, a touch screen, a touch pad, voice recognition hardware,dials, switches, buttons, a trackable probe, a foot pedal, a remotecontrol device, a scanner, a camera, a microphone, and/or a joystick.For example, the input device 46 allows a user to move one or morecomponents displayed on display device 44 based on one or moreconstraints, as described above, for planning the implant installation.

The communication interface 56 of the computing system 32 is coupled toa computing device (not shown) of the haptic device 34 via an interfaceand to the navigation system 36 via an interface. The interfaces caninclude a physical interface and a software interface. The physicalinterface may be any known interface such as, for example, a wiredinterface (e.g., serial, USB, Ethernet, CAN bus, and/or other cablecommunication interface) and/or a wireless interface (e.g., wirelessEthernet, wireless serial, infrared, and/or other wireless communicationsystem). The software interface may be resident on the surgicalcontroller 42, the computing device (not shown) of the haptic device 34,and/or the navigation system 36. In some embodiments, the surgicalcontroller 42 and the computing device (not shown) are the samecomputing device. The software may also operate on a remote server,housed in the same building as the surgical system 30, or at an externalserver site.

The system 30 also includes a tracking (or localizing) system 36 that isconfigured to determine a pose (i.e., position and orientation) of oneor more objects during a surgical procedure to detect movement of theobject(s). For example, the tracking system 36 may include a detectiondevice that obtains a pose of an object with respect to a coordinateframe of reference of the detection device. As the object moves in thecoordinate frame of reference, the detection device tracks the pose ofthe object to detect (or enable the surgical system 30 to determine)movement of the object. As a result, the computing system 32 can capturedata in response to movement of the tracked object or objects. Trackedobjects may include, for example, tools/instruments, patient anatomy,such as the targeted vertebrae and the cage 20 as tracked by trackingarray 22, implants/prosthetic devices, and components of the surgicalsystem 30. Using pose data from the tracking system 36, the surgicalsystem 30 is also able to register (or map or associate) coordinates inone space to those in another to achieve spatial alignment orcorrespondence (e.g., using a coordinate transformation process as iswell known). Objects in physical space may be registered to any suitablecoordinate system, such as a coordinate system being used by a processrunning on the surgical controller 42 and/or the computer device of thehaptic device 34. For example, utilizing pose data from the trackingsystem 36, the surgical system 30 is able to associate the physicalanatomy, such as the patient's spine, with a representation of theanatomy (such as an image displayed on the display device 44). Based ontracked object and registration data, the surgical system 30 maydetermine, for example, a spatial relationship between the image of theanatomy and the relevant anatomy. In the present method, becauseresection to form cavity 24 is being performed on two adjacent vertebraethat can move independently, both of the vertebrae must be registeredand tracked via the tracking system 36. This is accomplished byregistering portions of the vertebrae relative to the tracking array 22.Thus, the relationship between the tracking array 22 and the vertebraeis known, and the detection device is able to track the pose of thetracking array 22 to also track the associated vertebrae. In this way,by also tracking other aspects of the surgical system, such as thesurgical tool, the relationship between the tool and each of the targetvertebrae can be determined during the surgical procedure.

Registration may include any known registration technique, such as, forexample, image-to-image registration (e.g., monomodal registration whereimages of the same type or modality, such as fluoroscopic images or MRimages, are registered and/or multimodal registration where images ofdifferent types or modalities, such as Mill and CT, are registered);image-to-physical space registration (e.g., image-to-patientregistration where a digital data set of a patient's anatomy obtained byconventional imaging techniques is registered with the patient's actualanatomy); and/or combined image-to-image and image-to-physical-spaceregistration (e.g., registration of preoperative CT and MRI images to anintraoperative scene). Due to the profound landmarks present on thespine, registration of the spinal anatomy may be relativelystraightforward. The landmarks of the spine provide clear and accessiblepoints to use for registration of, for example, an image of thepatient's anatomy to the patient's anatomy in the physical space. Thecomputing system 32 may also include a coordinate transform process formapping (or transforming) coordinates in one space to those in anotherto achieve spatial alignment or correspondence. For example, thesurgical system 30 may use the coordinate transform process to mappositions of tracked objects (e.g., patient anatomy, etc.) into acoordinate system used by a process running on the computer of thehaptic device and/or the surgical controller 42. The coordinatetransform process may include any suitable transformation technique,such as, for example, rigid-body transformation, non-rigidtransformation, affine transformation, and the like.

The tracking system 36 may be any tracking system that enables thesurgical system 30 to continually determine (or track) a pose of therelevant anatomy of the patient. For example, the tracking system 36 mayinclude a non-mechanical tracking system, a mechanical tracking system,or any combination of non-mechanical and mechanical tracking systemssuitable for use in a surgical environment. The non-mechanical trackingsystem may include an optical (or visual), magnetic, radio, or acoustictracking system. Such systems typically include a detection deviceadapted to locate in predefined coordinate space specially recognizabletrackable elements (or trackers) that are detectable by the detectiondevice and that are either configured to be attached to the object to betracked or are an inherent part of the object to be tracked. In theembodiments shown in the figures, the trackable element (such astracking array 22) may include an array of markers having a uniquegeometric arrangement and a known geometric relationship to the trackedobject (the cage 20, and thus the adjacent vertebrae) when the trackableelement is attached to the tracked object. The known geometricrelationship may be, for example, a predefined geometric relationshipbetween the trackable element and an endpoint and axis of the trackedobject. Thus, the detection device can recognize a particular trackedobject, at least in part, from the geometry of the markers (if unique),an orientation of the axis, and a location of the endpoint within aframe of reference deduced from positions of the markers.

The markers may include any known marker, such as, for example,extrinsic markers (or fiducials) and/or intrinsic features of thetracked object. Extrinsic markers are artificial objects that areattached to the patient (e.g., markers affixed to skin, markersimplanted in bone, stereotactic frames, etc.) and are designed to bevisible to and accurately detectable by the detection device. Intrinsicfeatures are salient and accurately locatable portions of the trackedobject that are sufficiently defined and identifiable to function asrecognizable markers (e.g., landmarks, outlines of anatomical structure,shapes, colors, or any other sufficiently recognizable visualindicator). The markers may be located using any suitable detectionmethod, such as, for example, optical, electromagnetic, radio, oracoustic methods as are well known. For example, an optical trackingsystem having a stationary stereo camera pair sensitive to infraredradiation may be used to track markers that emit infrared radiationeither actively (such as a light emitting diode or LED) or passively(such as a spherical marker with a surface that reflects infraredradiation). Similarly, a magnetic tracking system may include astationary field generator that emits a spatially varying magnetic fieldsensed by small coils integrated into the tracked object.

Due to the size constraint and the sensitivity of the spinal anatomy,and other considerations, some of the more robust tracking mechanismsand markers may not be feasible for application in vertebral resection.In another embodiment, a mechanical tracking system, such as thatdisclosed in U.S. patent application Ser. No. 13/276,048 entitled“System and Method for Surgical Tool Tracking” filed Oct. 18, 2011,which is hereby incorporated by reference in its entirety, may be used.One such embodiment is shown in FIG. 8 , where a surgical instrument isoperatively coupled to a portion of the spine by a mechanical trackerconfiguration that is local to the operating theater (i.e., it isdirectly coupled between the surgical instrument 78 and the anatomydirectly around the subject of intervention, here the spinal column). Inthe depicted embodiment, the surgical instrument 78 is coupled to themechanical tracker by an instrument fastener comprising a kinematicinterface member 74 that is removably attached to a similar kinematicinterface member 72 comprising the distal end of the mechanical tracker.This distal kinematic interface member 72 preferably is coupled, via arotatable joint 70, to an elongate member 80 that has proximal anddistal ends. The proximal end in the depicted embodiment is coupled viaanother joint 82 to another elongate member 84 having proximal anddistal ends, the proximal end of which is coupled, via another joint 86,to a third elongate member 88 which has proximal and distal ends. Theproximal end of the most proximal elongate member 88 is coupled to akinematic interface member 90 by another rotatable joint 92. A skeletalfastener 94 is coupled between the vertebrae and the proximal end of themechanical tracker. One or more pins 96 are utilized to fasten theskeletal fastener 94 to the tissue of the vertebrae, while a kinematicinterface member 98 is interfaced with the similar kinematic interfacemember 90 of the proximal end of the mechanical tracker linkage. Withadequate degrees of freedom and ranges of motion at each rotatable joint70, 82, 86, 92 and an understanding of the rotational activity at eachsuch joint, it is possible to have a real-time or near-real-timeunderstanding of the three dimensional spatial positioning and rotationof the instrument relative to the subject anatomy. An understanding ofthe rotational activity at each joint may be achieved through the use ofjoint rotation sensors. In a preferred embodiment, the joint rotationsensors are encoders, such as precision digital encoders. Each encoderpreferably comprises or is operatively coupled to an encoder board,which may be coupled to a processing circuit and memory deviceconfigured to assist with operation of the encoder and enable it to beoperatively coupled, for example, via a wire lead or wirelesscommunication link, to a computing system, such as computing system 32.

This understanding of the rotational activity of the joints may beutilized, for example, to follow a specific surgical plan, such as, tocreate the cavity 24, having cavity portions 24 a, 24 b, on the twoadjacent vertebrae in accordance with a preoperative or intraoperativeplan to achieve the desired relationship between the two vertebrae.While the depicted embodiment shows three elongate members 80, 84, 88that are rotatably coupled to each other and to fastening configurations76, 94 other embodiments may contain more or less elongate membersand/or joints. Preferably the elongate members are light in weight forrelatively low inertial overhead during movement of the surgical tool78, and are substantially rigid, so that certain assumptions about theirdeflection during use of the mechanical linkage may be utilized (inanother embodiment, they may be more flexible if the flexibility can becharacterized with strain gauges or the like, so that deflection of thelinkage may be incorporated into the determination of positions andorientations of portions of the linkage).

Referring back to FIG. 6 , such a mechanical linkage configuration maybe utilized in corporation with the surgical system 30. The depictedinstrument 78 may be coupled to the mechanical linkage (and thereby thespine) of the configuration of FIG. 8 , while such instrument 78 alsoremains coupled to a base controller subsystem which comprises acomputerized controller such as a processor or microcontroller, andcarrying haptic device 34. Surgical system 30 and haptic device 34 mayalso be configured for use with the optical tracking system describedabove, utilizing at least tracking array 22 attached to cage 20.

The robotic arm of haptic device 34 may comprise one or more servomotors controlled by the computerized controller, and these servo motorsmay be selectively activated by the controller to enforce motionlimitations upon the surgical instrument 78, such as by providing hapticfeedback to an operator whose hand is trying to move the surgicalinstrument 78 held by haptic device 34 (and in some embodiments, themechanical linkage of FIG. 8 ), or by providing corrective motion as anoperator tries to move the surgical instrument 78 along a path thatstrays from a predetermined boundary planned according to the desiredplacement of the spinal plate 10 relative to the pertinent tissuestructures. Where mechanical linkage is used, preferably the kinematicsof the instrument support structure and the mechanical tracker linkagemay be configured to not spatially intersect or collide with each otherfor the useful ranges of motion of the surgical instrument 78 in theoperating workspace. Such a mechanical linkage configuration also may beutilized in corporation with a freehand surgical tool (i.e., notsupported by an instrument support structure).

The haptic device 34 may be the Tactile Guidance System™ (TGS™)manufactured by MAKO Surgical Corp., and used to prepare the surface ofthe patient's bone for insertion of the spinal plate 10. The hapticdevice 34 provides haptic (or tactile) guidance to guide the surgeonduring a surgical procedure. The haptic device is an interactivesurgical robotic arm that holds a surgical tool (e.g., a surgical burr)and is manipulated by the surgeon to perform a procedure on the patient,such as cutting a surface of a bone in preparation for spinal plateinstallation. As the surgeon manipulates the robotic arm to move thetool and sculpt the bone, the haptic device 34 guides the surgeon byproviding force feedback that constrains the tool from penetrating avirtual boundary.

For example, the surgical tool is coupled to the robotic arm andregistered to the patient's anatomy. The surgeon operates the tool bymanipulating the robotic arm to move the tool and perform the cuttingoperation. As the surgeon cuts, the navigation system 36, tracks thelocation of the tool and the patient's anatomy. In most cases, thehaptic device 34 allows the surgeon to freely move the tool in theworkspace. However, when the tool is in proximity to the virtualboundary (which is also registered to the patient's anatomy), the hapticdevice 34 controls the haptic device to provide haptic guidance (e.g.,force feedback) that tends to constrain the surgeon from penetrating thevirtual boundary with the tool.

The virtual boundary may represent, for example, a cutting boundarydefining a region of bone to be removed, such as cavity 24 for receivinga spinal plate 10, or a virtual pathway for guiding the surgical tool toa surgical site without contacting critical anatomical structures, whichmay be especially useful for the challenging approach given theanatomical structure of the lumbar spine region. The virtual boundarymay be defined by a haptic object and the haptic guidance may be in theform of force feedback (i.e., force and/or torque) that is mapped to thehaptic object and experienced by the surgeon as resistance to furthertool movement in the direction of the virtual boundary. Thus, thesurgeon may feel the sensation that the tool has encountered a physicalobject, such as a wall. In this manner, the virtual boundary functionsas a highly accurate virtual cutting guide. For example, the virtualboundary can represent a region of bone to be removed for properlyfitting the spinal plate 10 to the patient's target vertebrae as plannedthrough the planning procedure described below. Such virtual boundariescan help to ensure the efficient and accurate removal of portions of apatient's anatomy, which may include preparing bone and/or disc space,to accurately fit implant components based on a customized plan for thepatient. This also ensures that the actual placement of the spinal plate10 meets the constraints that were used in planning.

The surgical system 30 includes a visual display (e.g., the displaydevice 44) which can show the amount of bone removed during the cuttingoperation. Because the haptic device 34 utilizes tactile force feedback,the haptic device 34 can supplement or replace direct visualization ofthe surgical site and enhance the surgeon's natural tactile sense andphysical dexterity. Guidance from the haptic device 34 coupled withcomputer aided surgery (CAS), enables the surgeon to actively andaccurately control surgical actions (e.g., bone cutting) to achieve thetolerances and complex bone resection shapes that enable optimal andcustomized installation of implants, such as spinal plate 10.

In a preferred embodiment, surgical planning is accomplished using thesurgical system 30. For example, as described above, the surgeon may usethe surgical planning features of the computing system 32 to plan theplacement of the spinal plate 10 by placing a representation of theplate to a preoperative CT image (or other image or model of theanatomy), to define the virtual boundary of the region of bone to beremoved, or to define an area to create pre-drilled holes in the bonefor receiving engagement member 18. Planning the placement of the spinalplate 10 may be based on a desired relationship between two adjacentvertebrae. The plan involves planning resections on both of thevertebrae, independent of the other. The software enables the surgeon toview the placement of the plate 10 relative to the anatomy. Therepresentation of the plate used during surgical planning may representspinal plate 10, as described above, or represent any spinal platehaving its design in the computing system 32 database containing avariety of spinal plates that may be implanted on the patient's spine.Based on the planned placement of the spinal plate, the haptic device 34software generates one or more haptic objects, which create one or morevirtual boundaries representing, for example, a portion of bone to beremoved to sculpt cavity 24, including cavity portion 24 a on a firstvertebrae and cavity portion 24 b on a second, adjacent vertebrae, thelocation of pre-drilled holes, or critical anatomy to be avoided basedat least in part on the placement of the spinal plate. The hapticobjects may also create a virtual boundary representing an area of thevertebral disc space to be removed to perform a cervical or lumbardiscectomy. During surgery, the haptic object is registered to theanatomy of the patient, such as to the spine. By providing forcefeedback, the haptic device 34 enables the surgeon to interact with thehaptic object in the virtual environment. In this manner, the hapticdevice 34 haptically guides the surgeon during bone preparation tosculpt or contour the appropriate location of the bone so that a shapeof the bone substantially conforms to a shape of the spinal plate. Thehaptic device 34 may further haptically guide the surgeon to preparepre-drilled holes in the bone to conform with the areas of the spinalplate wherein engagement members may be received.

FIG. 9 describes an embodiment of a method of implanting a spinal plateon a patient's spine. In step 901, information about a spinal targetregion is displayed, for example, the relevant images of the patient'sanatomy acquired by a preoperative CT scan or a bone model and saved inthe computer system 32 may be loaded and displayed on display screen 44.Similarly, a representation of a spinal plate, such as spinal plate 10may be obtained. Information and images of the spinal plate 10 to beimplanted may also be displayed. Then, as described above, the spinalcage 20 is inserted between two adjacent vertebrae to achieve a desiredrelationship and obtain a desired alignment of the spinal area (step903). In step 905, also as described above, surgical planning may beperformed to determine and plan proper placement of the spinal plate onthe spinal target region to maintain the desired relationship betweentwo adjacent vertebrae, as well as create a plan for bone preparation.Step 907 includes defining a virtual cutting boundary for a cutting toolrelative to the virtual representations of the adjacent vertebraeaccording to the planned placement of the spinal plate 10. In step 909,a registration method is used to associate the physical anatomy, such asthe patient's spine, with the representation of the anatomy, which maybe achieved by using a tracking array 22 coupled to the spinal cage 20positioned between the vertebrae. The surgeon can then prepare the bonefor implantation of the spinal plate 10 according to the surgical planby manipulating the tool, such as a surgical burr, to sculpt cavity 24,including sculpting cavity portions 24 a, 24 b independently in each ofthe adjacent vertebrae and, optionally prepare pre-drilled holes 26 inthe bone (step 911). During bone preparation (step 911), the system maytrack a position of the surgical tool relative to the anatomy and/or thevirtual cutting boundary and provide feedback, such as haptic feedback,indicative of interaction between the cutting tool and the virtualcutting boundary to limit manipulation of the tool outside of thevirtual cutting boundary. Once the bone has been prepared, the surgeoncan remove the racking array 22, install the spinal plate 10, and securethe spinal plate 10 within cavity 24, preferably by at least oneengagement member 18 (step 913). The method of FIG. 9 may allowimplantation of a spinal plate 10 having a very low profile above thebone surface.

In other fusion applications such as ankle, hand/wrist, and other jointfusion procedures, and craniofacial fusion procedures, a similar methodcan be employed to obtain information about the target bones, to planplacement of a fusion plate to achieve a desired relationship, andprepare the target bones to receive a fusion plate to thereby help withmaintaining the desired relationship between the bones of the joint ortarget area. Though the present disclosure is directed to theabove-described spinal fusion procedure, it is contemplated that thesystems and methods described above could also be applied to variousother procedures, such as those listed.

The above-described systems and methods can be implemented in digitalelectronic circuitry, in computer hardware, firmware, and/or software.The implementation can be as a computer program product (i.e., acomputer program tangibly embodied in an information carrier). Theimplementation can, for example, be in a machine-readable storagedevice, for execution by, or to control the operation of, a dataprocessing apparatus. The implementation can, for example, be aprogrammable processor, a computer, and/or multiple computers.

A computer program can be written in any form of programming language,including compiled and/or interpreted languages, and the computerprogram can be deployed in any form, including as a stand-alone programor as a subroutine, element, and/or other unit suitable for use in acomputing environment. A computer program can be deployed to be executedon one computer or on multiple computers at one site.

Method steps can be performed by one or more programmable processorsexecuting a computer program to perform functions of the invention byoperating on input data and generating output. Method steps can also beperformed by and an apparatus can be implemented as special purposelogic circuitry. The circuitry can, for example, be a FPGA (fieldprogrammable gate array) and/or an ASIC (application-specific integratedcircuit). Modules, subroutines, and software agents can refer toportions of the computer program, the processor, the special circuitry,software, and/or hardware that implements that functionality.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor receives instructions and data from a read-only memory or arandom access memory or both. The essential elements of a computer are aprocessor for executing instructions and one or more memory devices forstoring instructions and data. Generally, a computer can include, can beoperatively coupled to receive data from and/or transfer data to one ormore mass storage devices for storing data (e.g., magnetic,magnetooptical disks, or optical disks).

Data transmission and instructions can also occur over a communicationsnetwork. Information carriers suitable for embodying computer programinstructions and data include all forms of non-volatile memory,including by way of example semiconductor memory devices. Theinformation carriers can, for example, be EPROM, EEPROM, flash memorydevices, magnetic disks, internal hard disks, removable disks,magneto-optical disks, CD-ROM, and/or DVD-ROM disks. The processor andthe memory can be supplemented by, and/or incorporated in specialpurpose logic circuitry.

To provide for interaction with a user, the above described techniquescan be implemented on a computer having a display device. The displaydevice can, for example, be a cathode ray tube (CRT) and/or a liquidcrystal display (LCD) monitor. The interaction with a user can, forexample, be a display of information to the user and a keyboard and apointing device (e.g., a mouse or a trackball) by which the user canprovide input to the computer (e.g., interact with a user interfaceelement). Other kinds of devices can be used to provide for interactionwith a user. Other devices can, for example, be feedback provided to theuser in any form of sensory feedback (e.g., visual feedback, auditoryfeedback, or tactile feedback). Input from the user can, for example, bereceived in any form, including acoustic, speech, and/or tactile input.

The above described techniques can be implemented in a distributedcomputing system that includes a back-end component. The back-endcomponent can, for example, be a data server, a middleware component,and/or an application server. The above described techniques can beimplemented in a distributing computing system that includes a front-endcomponent. The front-end component can, for example, be a clientcomputer having a graphical user interface, a Web browser through whicha user can interact with an example implementation, and/or othergraphical user interfaces for a transmitting device. The components ofthe system can be interconnected by any form or medium of digital datacommunication (e.g., a communication network). Examples of communicationnetworks include a local area network (LAN), a wide area network (WAN),the Internet, wired networks, and/or wireless networks.

The system can include clients and servers. A client and a server aregenerally remote from each other and typically interact through acommunication network. The relationship of client and server arises byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

The transmitting device can include, for example, a computer, a computerwith a browser device, a telephone, an IP phone, a mobile device (e.g.,cellular phone, personal digital assistant (PDA) device, laptopcomputer, electronic mail device), and/or other communication devices.The browser device includes, for example, a computer (e.g., desktopcomputer, laptop computer) with a browser.

One skilled in the art will realize the invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The foregoing embodiments are therefore to beconsidered in all respects illustrative rather than limiting of theinvention described herein. Scope of the invention is thus indicated bythe appended claims, rather than by the foregoing description, and allchanges that come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed is:
 1. A method, comprising: tracking one or more of aplurality of bones of a patient; adjusting a relationship between theplurality of bones to a desired rotation between the plurality of bones;creating an implant placement plan based on the relationship, theimplant placement plan comprising a placement of a plate across theplurality of bones; and robotically assisting preparation of theplurality of bones to receive the plate in accordance with the implantplacement plan.
 2. The method of claim 1, wherein the plurality of bonescomprise three or more bones.
 3. The method of claim 1, wherein creatingthe implant placement plan comprises planning a first cavity to besculpted at a first bone of the plurality of bones and a second cavityto be sculpted at a second bone of the plurality of bones, the firstcavity to receive a first portion of the plate and the second cavity toreceive a second portion of the plate.
 4. The method of claim 3, whereincreating the implant placement plan comprises planning the first cavityand the second cavity such that a top surface of the plate is planned tobe substantially flush with surfaces of the first bone and the secondbone.
 5. The method of claim 1, wherein robotically assistingpreparation of the plurality of bones to receive the plate comprises:tracking a pose of a robotic device relative to the plurality of bones;and controlling the robotic device based on the pose of the roboticdevice relative to the plurality of bones.
 6. The method of claim 5,wherein robotically assisting preparation of the plurality of bonescomprises providing force feedback via the robotic device.
 7. The methodof claim 1, wherein creating the implant placement plan comprisesdefining a virtual cutting boundary; and robotically preparing theplurality of bones includes confining a pose of a robotic device basedon the virtual cutting boundary.
 8. The method of claim 7, wherein thevirtual cutting boundary corresponds to one or more dimensions of theplate.
 9. The method of claim 1, wherein robotically assistingpreparation of the plurality of bones comprises creating a hole in afirst bone of the plurality of bones, the hole configured to receive anengagement member to engage the plate with the first bone.
 10. Themethod of claim 1, wherein creating the implant placement plan comprisesselecting a plate model from a database of plate models, the plate modelcorresponding to a shape and a size of the plate to be used in theimplant placement plan.
 11. A robotically-assisted surgical system,comprising: a tracking system configured to track one or more of aplurality of bones of a patient; a robotic device configured to assistmodification of the plurality of bones; and circuitry programmed to:obtain an adjusted relationship to a desired rotation between theplurality of bones; obtain an implant placement plan based on theadjusted relationship, wherein the implant placement plan comprise aplacement of a plate across the plurality of bones; and control therobotic device to assist the modification of the plurality of bones toreceive the plate in accordance with the implant placement plan.
 12. Therobotically-assisted surgical system of claim 11, wherein the pluralityof bones comprise three or more bones.
 13. The robotically-assistedsurgical system of claim 11, wherein the implant placement plancomprises a first cavity to be sculpted at a first bone of the pluralityof bones and a second cavity to be sculpted at a second bone of theplurality of bones, the first cavity to receive a first portion of theplate and the second cavity to receive a second portion of the plate.14. The robotically-assisted surgical system of claim 13, wherein thefirst cavity and the second cavity are planned such that a top surfaceof the plate is planned to be substantially flush with surfaces of thefirst bone and the second bone.
 15. The robotically-assisted surgicalsystem of claim 11, wherein: the tracking system is configured to tracka pose of the robotic device relative to the plurality of bones; and thecircuitry is programmed to control the robotic device based on the posefor the robotic device relative to the plurality of bones.
 16. Therobotically-assisted surgical system of claim 15, wherein the circuitryis programmed to control the robotic device to provide force feedback toa user of the robotic device.
 17. The robotically-assisted surgicalsystem of claim 11, wherein the implant placement plan comprises avirtual cutting boundary; and the circuitry is programmed to constrainthe robotic device based on the virtual cutting boundary.
 18. Therobotically-assisted surgical system of claim 17, wherein the virtualcutting boundary corresponds to a shape of the plate.
 19. Therobotically-assisted surgical system of claim 11, wherein the roboticdevice is configured to prepare a hole in a first bone of the pluralityof bones, the hole configured to receive an engagement member to engagethe plate with the first bone.
 20. The robotically-assisted surgicalsystem of claim 11, wherein the implant placement plan comprises a platemodel selected from a database of plate models, the plate modelcorresponding to a shape and a size of the plate to be used in theimplant placement plan.